Track Powered Lighting

[electricity_bill]

Hello

I have a Massoth powered DCC layout and I have been experimenting with lighting my carriages via the track power sourced from the loco. It works, but inevitably there is flicker from the loco’s pickups. I was thinking of putting a capacitor across the loco’s track input as per the “boosters” which are out there. Are there any issues with employing this idea in effect across a decoder and if not, what size capacitor should I use?
Bill

 

[idlemarvel]

You are talking about DCC keep alive and there have been many discussions about this on this forum over the years. In general there is no problem doing this but you have to have a switch to allow you to bypass the capacitor to program the decoder. Massoth decoders have a "software switch" which you can configure instead of a physical switch. Massoth provide a ready made keep alive module and there are instructions on their wiki for building your own if you can solder a few electronic components together. HTH.

 

[Greg Elmassian]

If you put an electrolytic capacitor across the track input, which is AC, it will most likely explode, so probably not a good idea.

Normally you take the track power, run it through a full wave bridge rectifier, then a BFC will work well there... you might also want to put a resistor in series with the BFC to tame the surge when it first get's power.

Greg

 

[Greg Elmassian]

You can also put an inductor in series with the BFC to isolate it from the programming signals... i.e. the inductor will stop the BFC from shorting the programming signals, but allow DC through.... see the end of the Zimo decoder sheets, it will give you the resistor, diode, and inductor and a small circuit in the Decoder keep alive section.

Greg

 

[PhilP]

First thing I would say, is the output sockets on the rear of loco's are usually track-power, so as Greg say's, do NOT put a capacitor across there!

Have you thought about a roller bearing pickup axle on the coach? - This could feed a rectifier, et al, complete with a little buffering.

 

[stockers]

Have a look here. Following the advice contained in here, ~I built very successful units for a relatively tiny price.
How do I make a simple power buffer for coach lighting. - G Scale Central

 

[Dan]

The initial charging of the capacitor can over load a digital system and the Zimo manual shows a resistor to limit the current charging the capacitor. The diode is used for discharging the capacitor into the decoder electronics.
Note that the newer Zimo MX69XX decoders a circuit built into the decoders, and the MX699's have a 16 volt super cap set built into the decoder.
These Zimo decoders omly need you to make sure the capacitors are discharged before trying to program them.